1. Field of the Invention
Polyoxyalkylene ether polyols hereinafter for convenience called polyols are commonly used in the production of urethane polymers. The said polyols are reacted with polyisocyanate in the presence of added catalyst and other materials to produce the urethane polymers which may be in the form of rubber-like elastomers, foams of flexible or rigid character, and the like. In order that urethane polymers of desired properties and characteristics are produced, it is importat that the polyols to be reacted with the polyisocyanate are essentially free of impurities which may function as undesirable catalysts or otherwise react undesirably in the urethane polymer reaction. Polyols as commercially prepared in the crude form contain alkali metal hydroxides or other metal salts. The normal concentration of catalysts range from 1000 to 3000 parts per million expressed as potassium. It is generally desirable to reduce this catalyst concentration to a level of about 10 parts per million or less.
2. Prior Art
There are a number of commercial practices employed for the removal of the catalyst impurities from polyols. Among these are included the neutralization of the catalysts by acids, forming insoluble salts and the removal of these salts by filtration. Other commercial practices involve centrifugation of a mixture of polyol, water and solvent. Ion exchange procedures may also be employed for the removal of catalysts. One commercial procedure for the removal of the catalyst without prior neutralization is treatment with a synthetic type adsorbent material such as magnesium silicate followed by the filtration of the resulting mixture. The process employing such a technique results in an adsorbent residue which contains an amount of polyol which may be equal to that of the adsorbent. The disposal of this spent adsorbent residue presents both ecological and safety problems. Generally speaking, the polyols themselves are not biodegradable and disposal of the adsorbent residue in a landfill is not desirable. The adsorbent wet with polyol, if allowed to remain exposed to the atmosphere, becomes pyrophoric and creates a safety hazard. Thus it is desirable to eliminate the necessity for the disposal of this spent adsorbent polyol residue. While the technical literature does teach the use of adsorbent for catalyst removal there is no teaching whatsoever that the adsorbent can be recycled and further use made thereof.